Carl paul goerz and emil von iioegh



BSO-+83 SR OR 5999700 I. DEAHSMAN.

' (No Model.) l C. P. GOBRZ 8v E. VON HOEGH. V COMBINED LENS EOE PHOTOGRAPHIE PURPOSES. i

No. 599,700. Patented Mar. 1, 1898.

order that this surface UNITED c STATES PATENT OFFICE.

GERMANY.

COMBINED LENS FOR PHOTOGRAPHIC PURPOSES.

SPECIFICATION forming part of Letters Patent No. 599,700, dated March 1, 1898.

Application filed July 6, 1897. Serial No. 643,507. (No model.)

To a/ZZ whom it may concern.-

Be it known that we, CARL PAUL GoEEz and EMIL von HEGII, citizens of the Kingdom of Prussia, and residents of Schneberg, near Berlin, in the Kingdom of Prussia and German Empire, have invented certain new and useful Improvements in Combined Lenses for Photographic Purposes, of which the following is a specification.

Our invention relates to an objective-lens of that class used for photographic purposes having for its object to obviat-e astigmatism and spherical-distortion effects and to increase the strength of light and sharpness of the impression of the lens.

The invention therefore consists in the assembling together of a plurality of lenses of dierent indices of refraction into a single lens.

The invention further consists in the parts and arrangements of parts, as hereinafter described and claimed.

The drawing illustrates a section of a lens constructed and arranged in accordance with our invention.

The objective-lens when constructed in accordance with our invention consists of a series of five lenses united together and contained in a case or envelop A, comprising the body a and the cap a', each lens possessing certain special qualities,acti ng together,when the several separate lenses are assembled, to meet the object in view.

As seen in the figure, five separate lenses are employed, designated by the referenceletters B, C, D, E, and F, and the index of refraction of the several lenses in round numbers are 1, 51; 1, 6l; l, 52; 1, 54; and 1, 6l, respectively.

In order to obtain the greatest possible strength of light, it is found that the first refracting concave surface b of the lens B should have as small a refraction as possible, (1, 51,) while the last convex surface f of the lens F should have as high a refraction as possible, (1, 61.); Furthermore, the first lens must be biconcave, so that at the second refractingsurface b there will be a cementing-surface acting as a collector of the light and compensating for the astigmatic aberrations, and in be as fiat as possible,

which is desirable to prevent curving of the image, it is necessary that at this second refracting-surface as large as possible a difference between the refractive indices of the material of the first and second lens be presentthat is, that the second lens C be formed of a glass of high refraction, (1, 61.) The second lens C must be biconvex, and to this must be applied a negative lens D of low refractive index, (1, 52,) so that at the third refractingsurface c a cementing-surface acting as a ligh tcollector opposed to the second one may be formed, which without increasing the astigmatism exercises a compensating influence upon the distortion which is the product of the other surfaces, so that by a right choice of the curvature of the surface c the distortion for a main ray falling sidewise will be completely neutralized. For the compensation of the spherical divergence the surface e is arranged. At this point there must not occur a difference in refractive index much greater than 1, 61 less 1, 54-4. e., 0, O7-because it must have an exactly-fixed depth, which is determined by the direction of the principal rays, which must encounter it under as small a refractive angle as possible, because here otherwise the distortion influences would be collected, which can no longer be compensated by the surface c. From this condition and from the condition already set forth-namely, that the last lens must be constructed of as highly-refractive a materialas possible (1, 61)-it becomes necessary to insert between the lens D and the lens F a further positive lens E of medium refraction, (1, 54:.) This lens E can be either biconvex or concave-convex, according to the positive or negative curvature of the surface e of the lens D. At this surface on account of the very slight difference of refractive index (about 0, O2) the errors of distortion and spherical divergence are very little influenced. The lens may be principally devoted to the complete removal of the chromatic divergence.

difficulty of bringing the lenses into the combination in exactly central position and of maintaining the same permanently in this )Vith the increase of the number of lenses the position is increased. In order to meet this difficulty, We have arranged in our five-lans 57'?,- 'foc i -.--systemtnat the negative lenses B, D, and F 1, 52; 1, 54; and 1A, 61; respectively,`substan 15 Y possess a greater diameter than the positive tially as described. lenses C and E inclosed by them and that the 2. An objective-lens comprising three nega.- l said negative lenses come in contact periphtive lenses and two positive lensesinterposed 5 erally by means of their projecting vertical and housed between the same, substantially edges; Theyconsequentlyconpletelyinelose as described. zo r the positive lenses, which are immovably in- In testimony that we claim the foregoing as closed between the same, andin tnrn inelosed our invention we have 'signed our names in by the oase A and are held in an immovable presence of two subscribing witnesses.

xo relation one to the other. CARL PAUL QOERZ.

W'hat we claim is-.. EMIL VON HOEGH. 1. An objective-lens comprising five lenses Witnesses: B, C, D, E, and F, each having an index of W. HAUPT, refraction substantially equal to 1, 51; 1,61; HENRY HASPER. 

